If it were just cap reasons we would have found another way. My guess is Manny was on tryout till Kesler got back.
You forget that Gillis was a good player till an injury took him out before he got a real chance. He knows what it's like to be cut down as well. I don't believe for a second that it was for malicious reasons.
As for 90 games? They wanted him to work it out, obviously but he didn't. He wasn't even 20% Malhotra. I liked him but he was a liability on the ice